Sir Arthur Conan DoyleNovelist, author of the Sherlock Holmes series of books

At the moment our human world is based on the suffering and destruction
of millions of non-humans. To perceive this and to do something to
change it in personal and public ways is to undergo a change of
perception akin to a religious conversion. Nothing can ever be seen in
quite the same way again because once you have admitted the terror and
pain of other species you will, unless you resist conversion, be always
aware of the endless permutations of suffering that support our society.